Re: [PATCH 1/2] dmaengine: ti: k3-udma: Respond TX done if DMA_PREP_INTERRUPT is not requested

[Péter Ujfalusi]

On 05/09/2022 06:02, Vaishnav Achath wrote:
> > Let me think about over the weekend... Do you have performance numbers for this
> > change?
> Thank you, yes we tested mainly for the SPI cases(Master and Slave mode), there
> we saw a peak delay of 400ms for transaction completion and this varied with CPU
> load, after adding the patch to not wait for DMA TX completion and use EOW
> interrupt the peak latency reduced to 2ms.

Thank you for the details.

> > If we make sure that this is only affecting non cyclic transfers with a in code
> > comment to explain the expectations from the user I think this can be safe.
> > \
> Sure I will add this in the next revision.

You can add my Acked-by when you send the next version:
Acked-by: Peter Ujfalusi <peter.ujfalusi@xxxxxxxxx>

> > > > > Signed-off-by: Vaishnav Achath <vaishnav.a@xxxxxx>
> > > > > ---
> > > > >    drivers/dma/ti/k3-udma.c | 5 ++++-
> > > > >    1 file changed, 4 insertions(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/drivers/dma/ti/k3-udma.c b/drivers/dma/ti/k3-udma.c
> > > > > index 39b330ada200..03d579068453 100644
> > > > > --- a/drivers/dma/ti/k3-udma.c
> > > > > +++ b/drivers/dma/ti/k3-udma.c
> > > > > @@ -263,6 +263,7 @@ struct udma_chan_config {
> > > > >        enum udma_tp_level channel_tpl; /* Channel Throughput Level */
> > > > >          u32 tr_trigger_type;
> > > > > +    unsigned long tx_flags;
> > > > >          /* PKDMA mapped channel */
> > > > >        int mapped_channel_id;
> > > > > @@ -1057,7 +1058,7 @@ static bool udma_is_desc_really_done(struct udma_chan
> > > > > *uc, struct udma_desc *d)
> > > > >          /* Only TX towards PDMA is affected */
> > > > >        if (uc->config.ep_type == PSIL_EP_NATIVE ||
> > > > > -        uc->config.dir != DMA_MEM_TO_DEV)
> > > > > +        uc->config.dir != DMA_MEM_TO_DEV || !(uc->config.tx_flags &
> > > > > DMA_PREP_INTERRUPT))
> > > > >            return true;
> > > > >          peer_bcnt = udma_tchanrt_read(uc, UDMA_CHAN_RT_PEER_BCNT_REG);
> > > > > @@ -3418,6 +3419,8 @@ udma_prep_slave_sg(struct dma_chan *chan, struct
> > > > > scatterlist *sgl,
> > > > >        if (!burst)
> > > > >            burst = 1;
> > > > >    +    uc->config.tx_flags = tx_flags;
> > > > > +
> > > > >        if (uc->config.pkt_mode)
> > > > >            d = udma_prep_slave_sg_pkt(uc, sgl, sglen, dir, tx_flags,
> > > > >                           context);

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Péter